An uncle of mine has a '92 Dakota 4wd , 5.2 Magnum, 4 spd auto. Above about 45 mph when cruising, it has a slight shudder. He's went through everything else (fuel/spark) and now discovered that when he unhooks the 3 wire OD/TC lock up it doesn't shudder, so it looks like the TC lock up clutch is toast. Before he rips it apart, I thought I'd double check on here to make sure it's not something else making the TC shudder. What "tells" the TC to lock up? Could it be a faulty switch that activates the lockup?

CONVERTER On my third . 170K miles

I agree, converter going away. Tell him to keep it unplugged, I've seen the converter clutch material go through the rear cooling line plug the hole at the tailshaft bearing and burn that bearing up, locking up the tailshaft causing the clutches in the trans to burn-up.

If you left the three wire plug unplugged you will not have lock-up but you also will loose overdrive. If you really wanted to leave the lock-up unhooked and drive it like an older converter with no lock-up you would have to disconnect the lock-up wire from the end of the connector or cut the lock-up wire because you need to have that plug plugged in for overdrive. The middle wire on the plug should be a 12 volt feed to the lock-up and overdrive solenoids and the two end wires are the ground controls for lock-up and overdrive to the PCM. I dont recommend unhooking the lock-up as you will loose some gas milage and it will set a code in the PCM. Ron

Thx for the replies guys, knew the TC was pooched but thought it prudent to double check. He left the plug in but disconnected the TC wire so he still has OD.

I'm confused. Why couldn't you just just disengage the OD by the switch on the dash?

Because the problem is the lock up in the converter not the OD in the tail shaft.

This way he still gets OD and the TC doesn't try to lock up

Thank you both for explaining
(I have a 93 Dak)